# Creep in Lead and Zinc Roofing

> Creep is the slow, permanent stretching of soft metals such as lead and zinc under their own weight and repeated thermal movement, causing thinning and tears.

- URL: https://roof.wiki/creep-in-sheet-metal/
- Topic: Problems, Repair & Maintenance
- Also known as: metal creep; lead creep; zinc creep
- Regions: Global
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Creep in Lead and Zinc Roofing." roof.wiki. https://roof.wiki/creep-in-sheet-metal/

## Key facts

- **Most affected metal:** Lead
- **Zinc countermeasure:** Titanium alloying (0.06-0.2%)
- **Lead countermeasure:** Limited bay sizes, drips, rolls, correct fixing

Creep is a gradual deformation of a material held under constant load. On roofs it affects soft, heavy metals, above all lead, and to a lesser degree zinc. Gravity pulls the sheet down the slope, and daily heating and cooling repeatedly stresses it, so over years the metal stretches, thickens at the bottom, thins at the top and can eventually crack or tear.

## Lead

US preservation guidance notes that lead roofs tear because of creep, the gravitational stress that moves the metal down the slope. Lead roofing practice in the UK manages creep by:

- limiting the size of each bay and piece for each lead code;
- breaking long runs with drips and rolls;
- fixing sheets at the top and along edges in patterns set out in the Lead Sheet Association manual;
- avoiding over-long pieces, which raise the risk of creep and fatigue cracking.

## Zinc

Unalloyed zinc can also creep. Architectural titanium-zinc includes about 0.06 to 0.2% titanium specifically to improve creep resistance, alongside copper for strength. Without it, zinc panels can thicken towards the eaves and slide gradually down the roof.

## Other metals

Copper, steel, stainless steel and aluminium are much less prone to creep at roof temperatures; their main movement concern is thermal expansion and contraction.

## Signs of creep

- Sagging or bulging sheets, thickening near lower edges.
- Fixings pulled through or elongated nail holes at the top of bays.
- Splits at fold lines and at the head of sheets.

Repairs usually involve replacing affected bays with correctly sized pieces rather than patching.

## Sources

1. Preservation Brief 4: Roofing for Historic Buildings — U.S. National Park Service, Technical Preservation Services. https://www.nps.gov/orgs/1739/upload/preservation-brief-04-roofing.pdf
2. Essential Zinc: Building for the Future — Continuing Education Center (BNP Media) / Umicore Building Products. https://continuingeducation.bnpmedia.com/courses/umicore-building-products-usa-inc/essential-zinc-building-for-the-future/2/
3. The top ten dos and don'ts of rolled lead sheet — RIBA Journal. https://ribaj.com/products/the-top-ten-dos-and-don-ts-of-rolled-lead-sheet